7 Handling of unknown, unforeseen, and erroneous Ethernet port management service and bridge management service data

24.5193GPP5G System (5GS)Release 16Stage 3Time-Sensitive Networking (TSN) Application Function (AF) to Device-Side TSN Translator (DS-TT) and Network-Side TSN Translator (NW-TT) protocol aspectsTS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

7.1 General

The procedures specified in clause 5 and clause 6 apply to those messages which pass the checks described in clause 7.

Clause 7 also specifies procedures for the handling of unknown, unforeseen, and erroneous Ethernet port management service (EPMS) and Bridge management service (BMS) data by the receiving entity. These procedures are called "error handling procedures", but in addition to providing recovery mechanisms for error situations they define a compatibility mechanism for future extensions of the EPMS or BMS.

Clauses 7.1 to 7.7 shall be applied in order of precedence.

Detailed error handling procedures in the TSN AF are implementation dependent and may vary from network to network. However, when extensions of EPMS or BMS are developed, TSN AFs are assumed to have the error handling which is indicated in this clause as mandatory ("shall") and that is indicated as strongly recommended ("should").

Also, the error handling of the TSN AF is only considered as mandatory or strongly recommended when certain thresholds for errors are not reached during a dedicated connection.

For definition of semantical and syntactical errors see 3GPP TS 24.007 [4], clause 11.4.2.

The procedures specified for TT are applicable for DS-TT or NW-TT.

7.2 Message too short or too long

7.2.1 Message too short

When a message is received that is too short to contain a complete message type information element, that message shall be ignored, cf. 3GPP TS 24.007 [4].

7.2.2 Message too long

The maximum size of an EPMS message sent by the DS-TT to the TSN AF or sent by the TSN AF to the DS-TT is 65535 octets. The maximum size of an EPMS message sent by the NW-TT to the TSN AF or sent by the TSN AF to the NW-TT is 65523 octets. The maximum size of a BMS message is 65531 octets.

7.3 Unknown or unforeseen message type

If the TT or the TSN AF receives an EPMS message with message type not defined for the EPMS or not implemented by the receiver, it shall ignore the EPMS message.

NOTE: A message type not defined for the EPMS in the given direction is regarded by the receiver as a message type not defined for the EPMS, see 3GPP TS 24.007 [4].

If the TT receives a message not compatible with the EPMS state, the TT shall ignore the EPMS message.

If the TSN AF receives a message not compatible with the EPMS state, the TSN AF actions are implementation dependent.

If the NW-TT or the TSN AF receives a BMS message with message type not defined for the BMS or not implemented by the receiver, it shall ignore the BMS message. If the DS-TT receives a BMS message with message type defined for the BMS or implemented by the receiver, it shall ingnore the BMS message.

NOTE: A message type not defined for the BMS in the given direction is regarded by the receiver as a message type not defined for the BMS, see 3GPP TS 24.007 [4].

If the NW-TT receives a message not compatible with the BMS state, the NW-TT shall ignore the BMS message.

If the TSN AF receives a message not compatible with the BMS state, the TSN AF actions are implementation dependent.

7.4 Non-semantical mandatory information element errors

When on receipt of a message,

a) an "imperative message part" error; or

b) a "missing mandatory IE" error

is diagnosed or when a message containing:

a) a syntactically incorrect mandatory IE;

b) an IE unknown in the message, but encoded as "comprehension required" (see 3GPP TS 24.007 [4]); or

c) an out of sequence IE encoded as "comprehension required" (see 3GPP TS 24.007 [4]) is received,

If the message is an EPMS message, the TT shall ignore the EPMS message. If the message is a BMS message, the NW-TT shall ignore the BMS message;

the TSN AF shall proceed as follows:

the TSN AF shall:

1) try to treat the message (the exact further actions are implementation dependent); or

2) ignore the message.

7.5 Unknown and unforeseen IEs in the non-imperative message part

7.5.1 IEIs unknown in the message

The TT shall ignore all IEs unknown in a message which are not encoded as "comprehension required" (see 3GPP TS 24.007 [4]).

The TSN AF shall take the same approach.

7.5.2 Out of sequence IEs

The TT shall ignore all out of sequence IEs in a message which are not encoded as "comprehension required" (see 3GPP TS 24.007 [4]).

The TSN AF should take the same approach.

7.5.3 Repeated IEs

If an information element with format T, TV, TLV, or TLV-E is repeated in a message in which repetition of the information element is not specified in clause 8, the TT shall handle only the contents of the information element appearing first and shall ignore all subsequent repetitions of the information element. When repetition of information elements is specified, the TT shall handle only the contents of specified repeated information elements. If the limit on repetition of information elements is exceeded, the TT shall handle the contents of information elements appearing first up to the limit of repetitions and shall ignore all subsequent repetitions of the information element.

The TSN AF should follow the same procedures.

7.6 Non-imperative message part errors

7.6.1 General

This category includes:

a) syntactically incorrect optional IEs; and

b) conditional IE errors.

7.6.2 Syntactically incorrect optional IEs

The TT shall treat all optional IEs that are syntactically incorrect in a message as not present in the message.

The TSN AF shall take the same approach.

7.6.3 Conditional IE errors

When upon receipt of an EPMS message the TT diagnoses a "missing conditional IE" error or an "unexpected conditional IE" error, or when it receives an EPMS message containing at least one syntactically incorrect conditional IE, the TT shall ignore the message.

When upon receipt of a BMS message the NW-TT diagnoses a "missing conditional IE" error or an "unexpected conditional IE" error, or when it receives a BMS message containing at least one syntactically incorrect conditional IE, the NW-TT shall ignore the message.

When the TSN AF receives a message and diagnoses a "missing conditional IE" error or an "unexpected conditional IE" error or when it receives a message containing at least one syntactically incorrect conditional IE, the TSN AF shall either:

a) try to treat the message (the exact further actions are implementation dependent); or

b) ignore the message.

7.7 Messages with semantically incorrect contents

When a message with semantically incorrect contents is received, the TT shall perform the foreseen reactions of the procedural part of clause 5 and clause 6. If, however no such reactions are specified, the TT shall ignore the message.

The TSN AF should follow the same procedure.